The present invention relates to a mobile terminal that can integrally move between a infrastructure network and an ad hoc network and to a method of controlling the same. An infrastructure network in which networks such as internets are interconnected via a relay node such as a router as well as an ad hoc network which has no relay node and is a network temporarily configured of only terminals are well known as aspects of a network.
In order to establish communications by connecting a mobile terminal to a network, the mobile terminal must have (1) a terminal address used in a network to be connected, or a network address of the network itself and (2) an opposite communication party's address.
With respect to the item (1), the dynamic host configuration protocol, DHCP, (for example, refer to Douglas E. Corner, “Internetworking with TCP/IP Volume I principles, protocols and architecture”, Third edition, 1995, Prentice-Hall, Inc.) is well known for an internet being an example of an infrastructure network. Moreover, with respect to the item (2), the domain name system, DNS, (for example, refer to Douglas E. Corner, “Internetworking with TCP/IP Volume I principles, protocols and architecture”, Third edition, 1995, Prentice-Hall, Inc.) is well known. In the DHCP, a DHCP server is set up that holds a terminal address or infrastructure network address to be allocated to a terminal. Necessary values such as terminal or network addresses for connection are requested to the DHCP server when a terminal is connected to a network. The DHCP server provides parameters to the terminal without troubles due to duplicate terminal addresses, based on the request from the terminal. FIG. 15 depicts such an operation. When the terminal 1 and the terminal 2 are connected to a network, they respectively broadcast DHCP Requests containing desired information. FIG. 15 shows an example in which the terminals 1 and 2 request a terminal address. In response to the DHCP Request message, the DHCP server transmits a DHCP ACK message containing supply information to the request sources. In FIG. 15, the DHCP server transmits two DHCP ACK messages, one containing an address 1 and the other containing an address 2, to avoid overlapping of a terminal address at the terminals 1 and 2.
In the internet, the DNS (Domain Name System) is used to detect the correspondence between the terminal name of a terminal and the terminal address. The DNS introduces a DNS server that manages the correspondences between the terminal's names of terminals to be managed and the terminal addresses and predetermines the procedure of making inquiries from a terminal to the DNS server and the procedure of making inquiries between servers. In most cases, the address of the DNS server managing a terminal is set to the terminal itself FIG. 16 depicts the case where the terminal 1 detects the terminal address of the terminal 2. The terminal 1 transmits a DNS Query message requesting the terminal address of the terminal 2 to the DNS server (the DNS server 1 in FIG. 16) registered. The DNS server 1 inquires the DNS server (the DNS server 2 in FIG. 16) managing the terminal address of the terminal 2. Then the DNS server 1 notifies the terminal 1 of the address 2 (DNS Reply message) when obtaining the terminal address of the terminal 2 (address 2).
The ad hoc network is configured of only terminals and does not have a server such as DHCP server or DNS server used in the infrastructure network. For this reason, even if the same procedure as that in the infrastructure network are used, communications cannot be accomplished by connecting the terminal to an ad hoc network. In order to accomplish communications according to the same procedure as that in the infrastructure network, a server function may be added to one of terminals connected to an ad hoc network. However, since this approach requires a special terminal with a server function, it is considerably poor in versatility. In order to improve the versatility, a procedure different from that in the infrastructure network may be defined in the ad hoc network so that the procedure can be selectively used according to an ad hoc network or infrastructure network to be connected. However, in the case of this procedure, the terminal must be reset when it moves between an ad hoc network and an infrastructure network according to the procedure for an infrastructure network and the procedure for an ad hoc network to be introduced thereto.